Extreme rainfall events in the UK may become up to four times more frequent by the 2070s

Extreme rainfall events in Britain could become up to four times more frequent over 50 years due to climate change, a new study suggests.

Met Office researchers created a new climate model to project the increase based on global warming reaching 7.

74°F (4.3°C) by 2100.

They also found that even with a smaller global temperature increase, it would still lead to nearly three times more heavy precipitation than today by the 2070s.

Experts say global warming is generally expected to intensify extreme rainfall globally, as warmer air can hold more moisture.

This heavy rainfall – defined by the study as 20 mm/h – is problematic because it can cause flash flooding, which causes water levels to rise rapidly and is particularly destructive.

Recent examples of such events in the UK include flash floods in Birmingham in May 2018, which resulted in fatalities, and in London in July 2021.

The authors said an increase in extreme rainfall would pose a challenge to local communities trying to cope with future flooding.

In England alone, an estimated three million properties are at risk from surface water flooding.

For this reason, the team added, they hope their research will help inform policy decisions in infrastructure design, land management and investments in flood protection.

Professor Elizabeth Kendon, from the Met Office and the University of Bristol, teamed up with colleagues to create a model that would study local future hourly extreme rainfall events of more than 20mm/h in the UK, both in the 1980s as in projections for the 2070s.

They found that 40 years ago there were an average of 11.9 such events per year, while that is expected to rise to 49.2 in half a century.

In Wales alone, extreme rainfall exceeding 20mm/h is expected to increase from 1.54 in the 1980s to 5.80 in the 2070s.

The corresponding figures for the East of England are 1.

06 to 3.35; Southwest 1.19 to 5.32; Southeast 1.16 to 3.57; Northeast 0.45 to 2.05; and Northwest 0.78 to 3.95.

Yorkshire and the Humber are predicted to have 2.77 such events per year through the 2070s, compared to 0.77 in the 1980s; West Midlands 2.27 and East Midlands 2.64.

Northern Ireland will not escape either, with projections rising to 3.21 from 0.53 40 years ago.

Northern Scotland goes from 0.54 to 5.30, the west from 0.67 to 4.42 and the east from 0.53 to 3.97.

Meanwhile, London is predicted to have 0.61 extreme rainfall per year through the 2070s, compared to 0.21 in the 1980s.

The authors wrote: ‘Regionally, future changes in the number of events will vary in excess of 20mm/hr, with the largest increases in the north of the UK.

“In Northern Scotland, for example, events are almost 10x more common in the 2070s than in the 1980s.

“

Their models show that ‘climate change leads to an average of 20 per cent more precipitation per hour in the UK and 40 per cent more regional registrations’.

In a high-emissions scenario, the researchers added, “the probability of extreme rainfall per hour will increase by about a factor of 4, which is significantly greater than suggested by previous generations of coarser-resolution climate models.”

“For every degree of regional warming, we see the intensity of extreme rainfall increasing by 5-15 per cent per hour and there are on average nearly nine more extreme events per year in the UK.

“Thus, changes in extreme rainfall events are expected to be pronounced even in medium to low emission scenarios.”

The new research is published in the journal Nature communication.